Thomas Mooney Sr. is a paunchy grandfather, an avid duck hunter who drives a Suburban and lives in McLean. Julian Epstein is a dashing bachelor, a hip-hop aficionado who drives a soft-top Jeep Sahara and lives in an Adams-Morgan loft he designed himself. Mooney hangs out at the Irish pub he owns in Alexandria. Epstein prefers the gym, the theater, the opera. Mooney's office has photos of Pope John Paul II and Rep. Henry J. Hyde (R-Ill.). Epstein's has photos of Louis Armstrong and President Clinton.

They make an odd couple, but as the House Judiciary Committee begins deciding the president's fate, Mooney and Epstein will share a crucial behind-the-scenes role. They are the top Republican and Democratic staff members for the committee, the unelected stage managers for the impeachment drama. And unlike their equally mismatched bosses, Hyde and Rep. John Conyers Jr. (D-Mich.), they get along extremely well.

Their close relationship will take on added importance in the weeks before the committee returns for public hearings on impeachment, as Hyde and Conyers struggle to hash out rules of engagement for a process launched only twice before by Congress. Mooney and Epstein will serve as the bridge between the chairman and the ranking Democrat, negotiating sticky issues such as which witnesses to subpoena, what facts to agree upon in advance and when to hold hearings.

At the same time, Mooney will help Republicans decide whether to narrow the scope of the inquiry and how to draft articles of impeachment against Clinton, while Epstein will help plot the Democratic strategy to defend the president. Both will also have to balance the desires of their bosses and other committee members with the demands of their party leaders. Speaker Newt Gingrich (R-Ga.), for example, is more anxious than Hyde for a wide-ranging investigation of Clinton, and Minority Leader Richard A. Gephardt (D-Mo.) has been less enthusiastic than Conyers about publicly defending the president.

Both Mooney, 55, and Epstein, 37, are creatures of Capitol Hill, pragmatic insiders who have spent their entire professional lives as congressional staffers and wield more institutional power than many of the lawmakers they serve. That influence was underscored yesterday when White House lawyers discussed the inquiry with the committee for the first time in a meeting with Mooney and Epstein, along with GOP and Democratic chief investigators David P. Schippers and Abbe D. Lowell. No members of Congress attended.

Mooney and Epstein both point to their friendship as proof that the political does not have to get personal. But neither is sure that their bonds of trust will bring a spirit of accommodation to the process. Civility, after all, is not the same thing as bipartisanship.

"Mooney's the best of the best," Epstein says. "He's never, ever misled me professionally, and I have great affection for him personally. . . . But I think we understand that we're going to be doing battle. This is going to be a very, very partisan process."

Then again, Epstein is known as a brilliant partisan tactician, while Mooney built his reputation as the draftsman for the bipartisan "Fragile Coalition" that swung the Judiciary panel against President Richard M. Nixon in July 1974. Unlike Epstein, a brash wunderkind who has never shied away from a fight, Mooney has been content to spend almost his entire career on the relatively placid intellectual property subcommittee. But now that Mooney has taken over the full committee staff, returning to the issue that launched his career as a bridge-builder during Watergate, even he is expecting an ugly scrap.

"You know, during those meetings of the Fragile Coalition, we talked about what was best for the country," Mooney recalls. "I mean, sure, we threw doughnuts around the room, but we felt like we were conducting serious business. I don't know if we're going to see that again."

The Mooneys of Lima, Ohio, were Irish Catholics and New Deal Democrats. Tom's parents worked in local factories -- his dad building tanks, his mom packing cigars -- and Tom and his seven siblings expected to do the same. But Tom, prodded by a local priest, became the first Mooney to attend college, paying his way through St. Joseph's in Rensselaer, Ind., by moonlighting as a janitor. He then moved on to Ohio Northern Law School in Ada, Ohio, teaching English and coaching football to make ends meet.

The priest then suggested that Mooney and his wife, Melinda, a nurse, should think about living in Washington. So Tom packed up his Buick station wagon, drove straight to the Skyline Motel in the shadow of the Capitol and begged his local congressman for a job. The congressman happened to be a Republican. And he happened to know of an opening for a law clerk on the House Judiciary Committee.

"I remember pulling back the curtains in the motel and seeing the Capitol," Mooney says with a grin. "I didn't know anyone in town. I didn't know anything about the committee. All I could think was: 'What the hell have I done?' "

Mooney quickly buried himself in the substance of legislation, a habit that paid off five years later when John W. Dean III, his former boss at the committee, offered him a new job as a lawyer in the White House counsel's office. Mooney declined, content to keep working on prison reform issues. The Watergate scandal exploded a month or so later, and Dean eventually landed right in the middle of it.

So did Mooney. At the time, he was already the Republican counsel to the subcommittee dealing with copyrights and patents, a job he held until this March. When his boss, then-Rep. Tom Railsback (Ill.), convened the Fragile Coalition of four Republicans and three conservative Democrats to discuss impeachment, Mooney became the group's unofficial staffer. He scrawled the first draft of the first article of impeachment eventually adopted by the committee, and helped draft the second article as well.

"Tom was a perfect diplomat," says former representative M. Caldwell Butler (R-Va.). "He helped organize everything we did. I can't think of anyone I'd rather see in that position today."

In 1974, the coalition essentially shot down articles of impeachment about tax fraud and the "secret" bombings of Cambodia, arguing that they were unprovable distractions from the heart of the case against Nixon. Last week, when Hyde said he may streamline the 15 allegations announced by Schippers into a few "core charges" against Clinton, some readers of Republican tea leaves suspected that the old coalition's staff member was at it again.

By all accounts, he is a genuine consensus-builder, hailed even by committee Democrats as one of the nicest men on Capitol Hill. He has been married to Melinda for 32 years, and his office is cluttered with pictures of his four children and three grandchildren. "You'll never hear a disparaging word about Tom Mooney," says Rep. William D. Delahunt (D-Mass.). Robert Raben, a counsel for Rep. Barney Frank (D-Mass.), remembers that when his group of gay Hill staff members wanted to screen a controversial documentary in a Judiciary hearing room, Mooney not only defended their right to do it but stopped by to make sure no one was hassling them. "Tom's one of those rare people where what you see is what you get," Raben says.

There is no obvious Republican or Democratic way to write patent law, so Mooney was able to avoid many of Judiciary's partisan food fights on the intellectual property subcommittee. But ever since Hyde named him general counsel and chief of staff for the full committee in March, Mooney has been embroiled in emotionally charged issues: partial-birth abortion, affirmative action, doctor-assisted suicide, gun control.

Now Mooney is the GOP point man for the Monica S. Lewinsky mess. His Democratic admirers describe him as "tortured" by the divisive case and cite him as a potential moderating influence on Republicans who have already decided to impeach the president.

But Mooney does not sound tortured. "At least Nixon just covered up the conduct of his subordinates; Clinton covered up his own conduct," Mooney says. "Nixon lied to the public, but never under oath. Clinton lied to the public, and in a deposition, and to the grand jury! Are we supposed to ignore that? Or do the laws of this country apply to everybody? I guess we'll see."

Mooney's proudest achievements since Watergate are helping to rewrite the copyright code in 1978 and the primary trademark law in 1988. Not very sexy, but certainly substantive.

Epstein is prouder of his strategic accomplishments. During the Waco hearings, he shifted attention away from the missteps of Clinton administration law enforcement officials by summoning a Branch Davidian girl to testify about the brutality of cult leader David Koresh. During the debate over the proposed balanced-budget constitutional amendment, he helped choreograph the strategy of accusing Republicans of endangering Social Security. As Judiciary's chief minority counsel and staff director, he has steered Democrats toward the center on "wedge" issues such as crime and affirmative action.

"I believe in smart politics," he says. "I don't believe in losing fights. If you think tactically and stay focused, you can snatch victory from the jaws of defeat."

And that is exactly his goal for the impeachment inquiry. His job, he says, is to coordinate Democrats, to keep them unified against impeachment, to change the subject from Clinton's misbehavior to independent counsel Kenneth W. Starr's exhaustive excavation of sexual details. The defection of only 31 Democrats to the GOP plan for the impeachment probe showed, Epstein says, that the president's defenders are winning the public relations battle over "Starr's smut."

"We were aggressive. Unified. On message," he says. "Tactically, we hit it just right."

Epstein says he inherited his competitive political instincts from his Jewish father, a public health advocate. His creative side came from his Irish-Italian mother, an opera singer. He grew up in the Democratic stronghold of Boston, where he became a standout hockey player and an accomplished painter. He attended the University of Michigan and after graduation went straight to the personal staff of Conyers, an iconoclastic black Democrat from Detroit. By 1989, when Epstein was 27, he was already the staff director overseeing investigations for the Government Operations Committee, one of the the youngest staff directors ever. He was also attending Georgetown Law School at night.

With his elegant designer suits, fast-lane lifestyle, unapologetic gamesmanship and golden-boy reputation, Epstein is at times a magnet for resentment on the Hill, derided by one aide as "Machiavelli in Armani." But Mooney and other Republicans who have worked with Epstein say that for all his partisanship, he is unfailingly polite and honest. "There were a lot of people who thought he was Machiavellian, but he was always a straight shooter with me," said Alan Coffey, Mooney's predecessor. "He's very savvy -- that's his job."

For now, Hyde, Mooney and Schippers are controlling the impeachment process, but they are eager to avoid open declarations of partisan warfare. So Mooney is talking to Epstein four or five times a day. Epstein then spreads the news to Conyers, other committee Democrats, party leaders and often White House officials. All of them seem to think Epstein -- who had planned to leave the Hill this fall for Stanford to write a dissertation about the inner workings of Congress -- is the right person to be in the middle of the action.

"He's the perfect guy for that job, because he's a great tactician," says Don Goldberg, who worked with Epstein at Government Operations and is now the White House legislative liaison handling the inquiry. "Julian knows how to position the Democrats. . . . He doesn't let philosophy get in the way of doing his job."

On Sept. 9 at 3:45 p.m., Mooney took the call that transformed American politics. Jackie M. Bennett, Starr's deputy, was on the line, and the 18 boxes of material that made up Starr's referral to Congress were on the road.

Mooney then made three quick calls of his own: to Gingrich, the House sergeant at arms and Epstein. "We haven't taken a breath since," Mooney says.

The committee that Mooney and Epstein help run does not allow for much breathing room. The panel's 21 Republicans are almost all white, male, Christian conservatives. The 16 Democrats are mostly urban Jews or blacks who tilt to the left. All but two members are attorneys, and to put it mildly, they tend to argue a lot.

Still, Hyde says he believes the committee will rise to the occasion, the way it did during Watergate. "We're a committee of polar opposites, but we get along pretty well," he says. "Tom and Julian really set the tone."

After all, a bipartisan "breakfast club" of 10 committee members recently began holding meetings. And the midterm elections will be over next month. "Watergate wasn't bipartisan until the very end," Mooney says. "Maybe the same thing can happen to us."

But even Mooney seems to have hardened his position, arguing that "none of this crap would have happened" if Clinton hadn't lied. "It's a tough situation," Hyde says wearily. "People get painted into a corner by saying things that don't leave much room for maneuver. It's true on both sides. Maybe if we had more indecision, we'd have more hope of coming together."

In his more contemplative moments, even Epstein is critical of the supremacy of partisan politics. He says that with a few minutes alone, away from the polls and the posturing, he and Mooney could make this whole thing go away.

It starts to sound strangely plausible, the idea that a common-sense conversation between Mr. Inside and Mr. Even Further Inside could end this. "There's too much conflict in Washington," he sighs. "We ought to spend less time thinking about what's going to look good on the evening news and more time working together for real solutions."

Just as quickly, though, Epstein snaps out of his soliloquy. "We're not there yet," he says. "We're nowhere near there."